Coronary artery disease, which is the leading cause of death in the United States, can occur when arteries become clogged or constricted and blood flow is reduced to the heart. Angioplasty is a procedure that dilates the arteries and restores normal blood flow to the heart. Stents are tiny metal coils inserted in the arteries during most angioplasty procedures, which support the blood vessels after they have been dilated and prevent re-occlusion.